وَعَنْهُ قَالَ: «نَهَى رَسُولُ اَللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: أَنْ يَبِيعَ حَاضِرٌ لِبَادٍ، وَلَا تَنَاجَشُوا، وَلَا يَبِيعُ اَلرَّجُلُ عَلَى بَيْعِ أَخِيهِ، وَلَا يَخْطُبُ عَلَى خِطْبَةِ أَخِيهِ، وَلَا تُسْأَلُ اَلْمَرْأَةُ طَلَاقَ أُخْتِهَا لِتَكْفَأَ مَا فِي إِنَائِهَا»
The Messenger of Allah (sallallahu alayhi wa sallam) forbade, a city-dweller to sell for a man from the desert; one to bid against another (to raise the price); that someone sell (his product) by canceling the sale of his brother; to propose (marriage) to a woman after his brother has done so; or a woman to ask to have her sister divorced in order to deprive her of what belongs to her.
Bulugh al-Maram 923, Book 7, Business Transactions, Hadith 34. 1 min read